Within the field of infrared (IR), or thermal, imaging, it is common to capture IR radiation emitted from an observed scene with an IR imaging system, also referred to as a thermography arrangement, e.g. in the form of an IR camera, and to process the IR radiation information into a visible light image that is typically shown to a user on a display of the system.
A problem with this is that it is difficult for a user of the imaging system to discern and analyze what is being shown on the display, since the image representing the IR radiation information often has a low resolution and the display unit typically is quite small.
The user of the IR imaging system may choose to save one or more images and transfer them to another unit, such as a computer, for later display. In this way, the one or more images may be presented on a larger display. However, this leads to a delay from the moment when the IR radiation is detected to the moment when the detected information is presented to the user, in other words, the analysis of the detected information may not be performed on site. Furthermore, it may be hard for the user to retrospectively relate the information displayed on a computer display to the real world scene where the IR radiation detection has been performed.
In a typical use case of an IR camera an operator would like to analyze the characteristics of one or more objects or surfaces in an observed scene by detecting the temperature of different points or parts of the object. The operator captures an IR image and then compares the IR image of the scene with the real world scene. In this process the operator has to translate or interpret the image information to the reality by comparing what is displayed on a typically small display of the IR camera with the real world scene, in order to understand how the image information on the display relates to the real world scene, with the entailing effort, error source and delay there may be.
Some pieces of related art address these problems by providing a combination of an IR detector or IR camera and a visible light projector that enables display of a larger visible image on site, the visible image being projected for instance onto a flat surface of the observed scene. This related art is devised to generate a visible light image dependent on the IR radiation and to project a visible interpretation of the IR radiation directly onto the observed scene. Thereby it is made possible to use the IR radiation information in a more close connection to the observed scene.
The production of projection devices of small sizes is becoming increasingly common as the technology advances and smaller construction components are available. Such “miniature” projectors may therefore for example be used in combination with handheld devices, such as mobile communication devices with imaging capabilities or imaging systems. This development makes it more feasible also to produce handheld IR cameras with a projector. However, in related art there remains to develop the methods for integrating an IR camera with a projector.
Since the capturing of IR information in the form of an IR image and the projection of a visual image that is a visual representation of the IR image are performed by different and physically separated components, the optical axes of the components are typically at a distance from each other and an optical phenomenon known as parallax will arise. To compensate for the parallax error, the images must be aligned. Traditionally alignment is achieved by adaptation of optical elements in the imaging system, for instance focus lenses or beam splitters. Alignment using optical or other physical elements in the imaging system requires space in the imaging systems and may be hard to fit. Furthermore, the inclusion of additional or specially adapted elements in the imaging system renders a higher production cost.
Thus, there exists a need for improved alignment of a visual representation of IR radiation information to detected IR information.